Western blacklegged tick

Family: Ixodidae. Genus: Ixodes. Hard tick. Taxonomic authority: Cooley and Kohls, 1943. Life stages: egg, larva, nymph and adult.

Adult females have a dark anterior scutum and reddish-orange posterior body when unfed. Ixodes ticks lack eyes and festoons and have an anal groove anterior to the anus. Expert examination may be needed to separate related Ixodes.

Long mouthparts; no eyes or festoons; anal groove anterior to the anus. Adult females have a dark scutum and reddish posterior body. Engorgement substantially changes appearance.

Closely resembles Ixodes scapularis. Pacific coast occurrence is useful context but is not sufficient for species confirmation.

Photographs alone cannot always confirm this species. Geographic location, host and colour are supporting context, not conclusive identification; expert morphological examination may be required.

Adult females have a small anterior scutum and expandable posterior body; adult males are smaller and more uniformly dark because the scutum covers most of the dorsum.

Three-host hard-tick life cycle. Larvae and nymphs often feed on lizards, birds and rodents; adults more commonly feed on deer and other large mammals.

Human encounter timing varies across the Pacific coast range. CDC reports nymphs and adult females more often on people; use current regional surveillance for seasonal interpretation.

Found along the Pacific coast of the United States, particularly northern California. CDC maps separately show projected suitable habitat and counties meeting an established-population threshold.

A confirmed western U.S. vector of Borrelia burgdorferi and Anaplasma phagocytophilum. Pathogen prevalence and human disease risk vary geographically and are not equivalent to tick presence.

Feeds on wildlife and domestic animals. Veterinary significance varies with host and pathogen geography.

CDC identifies Ixodes pacificus as a vector of Borrelia burgdorferi and the principal West Coast vector of Anaplasma phagocytophilum.

Nymphs and adult females commonly bite people within the species range. It is among the most frequently recorded human-biting U.S. tick species.

Feeds on domestic animals and wildlife; relevance varies across the Pacific coast range.

Prevent tick bites by using current public-health guidance, walking in the centre of trails where practical, using appropriate repellents, treating clothing or gear where suitable, and performing thorough tick checks after exposure.

Remove an attached tick promptly with fine-tipped tweezers or a purpose-designed tick-removal tool. Grasp close to the skin and pull upward steadily without twisting or crushing the tick. Seek professional medical or veterinary advice when symptoms or concerns arise.